Game Boy modified to play GBA, GBC, and of course GB carts. Since CRTdrone replaced its internals with GBA SP parts, it also features a rechargeable battery!
Even with compatibility for all those games, I imagine it’s difficult to play titles that require the GBA’s shoulder buttons. Still, this vibrant color display on an old Game Boy will certainly turn a few heads.
See also: More hardware mods (mostly Game Boys)